Immunochemical Investigation of Predation on Marine Microzooplankton

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Quantitative understanding of the link between microbial loop organisms and suspension-feeding macrozooplankton is one of the central issues in zooplankton ecology today. This research project will utilize a newly developed immunochemical probe to ciliate protozoa to investigate this link in laboratory and field studies. The probe overcomes the difficulties with conventional methodologies. It permits predation on microzooplankton to be studied without artifacts of collection, concentration, incubation, or preservation. The following hypotheses will be tested: 1. H0: A cross-shore gradient exists in the ciliate link to suspension-feeding copepods, from an inshore upwelling domain to an offshore, stably stratified domain. 2. H0: Temporal variations occur in the ciliate link to suspension-feeding copepods, with increased significance during relaxation of upwelling events. 3. H0: Interspecific differences exist in the importance of ciliates to co-occurring species of suspension-feeding copepods. The study will contrast 3 major suspension-feeding copepods in the California Current System: an epipelagic species (Calanus pacificus californicus), a mesopelagic species (Eucalanus californicus), and a strong vertical migrant (Metridia pacifica). Laboratory experiments will develop additional antisera and characterize predation rates on different ciliate taxa. Field research will be conducted in conjunction with the CalCOFI program. These cruises will address cross-shore and temporal variations in the ciliate link to suspension-feeding copepods, utilizing immunochemical dot blots, gut fluorescenec, and Iatroscan lipid analyses. Additional cruises will address diel and vertical variations, to examine any interspcific differences in the significance of this linkage to coexisting species of suspension-feeding zooplankton.